1. Technical Field
The present invention relates to a biological information measuring apparatus.
2. Related Art
According to the related art, a measuring apparatus which is installed at a site such as the wrist with a band or the like and measures biological information such as the pulse waves and pulse rates of the wearer, and a wristwatch-like electronic apparatus having the function of measuring such biological information, are known (see, for example, JP-A-2010-110634 and JP-A-2006-271610). In the case of such apparatuses (measuring apparatus and electronic apparatus), a case unit (main body unit) having a display unit is installed on the wrist with two bands extending on both sides of the case unit. On the back side of the case unit (opposite side of the display unit), a detection unit (sensor) for optically detecting pulse waves is arranged.
In such apparatuses, the detection unit needs to be in tight contact with the arm in order to measure biological information stably. More specifically, the apparatus needs to be wearable in the state where the case unit is in tight contact with the site where the apparatus is installed, for example, the wrist, even if the circumferential size or cross-sectional shape of the site differs from wearer to wearer. Also, in order to continue measuring biological information, the whole apparatus including the bands needs to have a small-sized and lightweight configuration so that the wearer can wear the apparatus comfortably for a longtime with little burden.
To cope with this need, JP-A-2010-110634 discloses a configuration in which each of the two bands extending on both sides of the case unit (device main body) is provided with an expansion/contraction part capable of expanding and contracting in the longitudinal direction of the band. According to this, the detection unit can be brought in tight contact with the arm by the restoring force in the expansion and contraction of the expansion/contraction part. JP-A-2006-271610 discloses a configuration in which one band (band piece) is made up of two band members, with the two band members connected together via a connection member with high expansion/contraction ability. According to this, the detection unit can be brought in tight contact with the arm by the restoring force in the expansion and contraction of the connection member.
In such related-art apparatuses, as the detection unit (sensor) is brought in tight contact with the wrist, the bands are brought in tight contact with the wrist as well. Therefore, if the apparatus is worn on the wrist for a long time, the wearer's sweat and inevitable moisture in living (for example, drops of water after washing the hands) accumulate between the bands and the skin, causing the problem of discomfort experienced by the wearer.
To cope with this problem, it is effective to provide a groove on the surface of the bands that contacts the wrist, for example, so as to reduce the contact area between the bands and the skin or to release the sweat and moisture outside. In each of JP-A-2010-110634 and JP-A-2006-271610, FIG. 1 shows a groove-like site extending in the longitudinal direction of the band, in a center part on the surface of the band that contacts the wrist. However, the shape of the groove-like site, including the depth dimension, length dimension or width dimension, is not described in the text at all.
However, in the related-art apparatuses, if the groove shape is not properly set, there is a risk that the sweat and moisture cannot be released outside sufficiently or that the strength (durability) of the bands may not be sufficient.
Specifically, if the width of the groove is too narrow or the depth of the groove is too shallow, it is difficult for the sweat and moisture to escape outside from the tight contact part between the bands and the skin, and consequently the sweat and moisture remaining in the tight contact part between the bands and the skin cause discomfort to the wearer. In other words, the sensation of wearing experienced by the wearer is impaired and the wearer ends up feeling stressed about long-time wearing. In some cases, the wearer may give up wearing the apparatus. If the wearer gives up wearing the apparatus in this way, biological information (health state) such as the pulse waves of the wearer can no longer be measured (grasped). Also, if the width of the groove is narrow or the depth of the groove is shallow, the flexibility of the bands is impaired. Therefore, the durability with time of the bands may fall and damage such as cracking may occur.
Meanwhile, if the width of the groove is too broad or the depth of the groove is too deep, the strength of the bands falls, leading to damage to the bands, or deformation of the bands due to an impact or acceleration (G) applied to the apparatus at the time of running, for example. Therefore, the tight contactability between the detection unit (sensor) and the skin may fall. Consequently, biological information (health state) such as the pulse waves of the wearer can no longer be measured (grasped) accurately.